This image of the southeastern part of
Lake Superior shows near total ice-cover.
It is difficult though to see the difference between the white clouds
and the snow in this satellite image. Roll your mouse over the image to
see a multi-spectral view that uses color to enhance the difference between
the clouds and the snow and ice. In the second image the snow and ice
are pink and red while the clouds are blue and white.

According to the National
Ice Center, Lake Superior was 90-95% iced over at the beginning of
this week. In some areas, the ice is only a few centimeters (1 inch) thick,
but large areas of the lake have 30-70 cm (12-28 inches) of ice, according
to the National Ice Center. The last time the lake has been this ice covered
(96%) was in 1994. The lake froze to almost 100% was in 1996, but the
last time it was completely ice-covered was in 1979. According to the
Climatology
Working Group at the University of Minnesota, Lake Superior freezes
completely about every 20 years. The last recorded ice-over was in 1962.
The cause is the month long record cold temperatures over the area. This
was the coldest March in over 100 years in Canada.

Two other lakes, Huron and Erie are also frozen, but
these lakes are more shallow and the ice was as deep as 60 cm (24 inches)
over most of Lake Erie by last week, as can be seen on this CIMSS
Map animation of the Great Lakes. This contrasts with the mild winter
of 1999 when all of Lake Erie and most of most of Lake Superior was open
water by the same week of March. The thick ice is expected to delay the
beginning of the shipping in the Great Lakes until late April because
tugs have to wait until the ice is thin enough for them to break through.

These satellite images were taken using Moderate-Resolution
Imaging Spectroradiometer (MODIS). MODIS is an instrument that measures
biological and physical processes in the satellite images it photographs.
MODIS was launched on the EOS PM and TERRA
satellites in 1999. Some other data MODIS can provide scientists with
includes chlorophyll concentrations, vegetation and land cover types,
cloud and snow, and fire cover.